Updated at 12:34 p.m.
Sen. Harry Reid, D-Nev., the Democratic leader in the Senate, said he won't seek re-election next year.
"My friend Sen. [Mitch] McConnell, don't be too elated. I'm going to be here for 22 months," he said referring to the Senate majority leader from Kentucky. "And you know what I'm going to be doing? The same thing I've done since I first came to the Senate."
He later told Nevada Public Radio that he was endorsing Sen. Chuck Schumer of New York, the Senate's No. 3 Democrat, to succeed him as minority leader.
"He will be elected to replace me in 22 months," he told the public radio station. "I think one reason that will happen is because I want him to be my replacement."
Reid's announcement, made in a video posted on YouTube, comes after the Senate minority leader, a former amateur boxer, suffered serious injuries to his eye and face following an accident at his Las Vegas home Jan. 1. Reid called them "an inconvenience" but said, "trust me they are nothing compared to some of the bruises I got when I was fighting in the ring." He told The New York Times, which first reported on the retirement, that neither the injuries nor his new position as Senate minority leader prompted the decision.
"But," he said in his message, "this accident has caused Landra and I to have a little downtime. I have had time to ponder and to think. We've got to be more concerned about the country, the Senate, the state of Nevada than about ourselves. And as a result of that I'm not going to run for re-election."
Reid, a former head of the Nevada gaming commission, was first elected to the House of Representatives in 1982. He was elected to the Senate in 1988 and became Senate majority leader in 2005, a position he held until Democrats lost the chamber in 2014.
Here is a video announcing his decision.
In a statement, President Obama called Reid a "fighter."
"As the leader of the Senate Democrats during my time in office, Harry has become not only an ally, but a friend," Obama said. "I'm proud of all we have accomplished together, and I know the Senate will not be the same without him."
Obama also called in to Nevada Public Radio, when the station was interviewing Reid, to praise the Senate minority leader. He said Reid's work saved the U.S. from a depression after the financial crisis of 2008 and lauded his work on the Affordable Care Act, Obama's signature achievement.
"I think when the story is written, and when all is told, you're going to have somebody who has done more for Nevada and for this country as anybody who has ever been in the Senate," Obama said. "And I could not be prouder of him. ... He's been one of my best partners and best friends."
(You can listen to KNPR's full interview with Reid today in the station's State of Nevada program.)